Tamayo had been convicted of the fatal shooting of Houston Police Officer Guy Gaddis in 1994. At the time of his death, Gaddis was just 24 years old.

Approximately 17 minutes after the lethal dose of pentobarbital was administered at 9:32 p.m. CST, Tamayo was pronounced dead. The lethal injection had reportedly been delayed for more than three hours while the U.S. Supreme Court considered last-minute appeals.

Tamayo was the first person to be executed in Texas in 2014.

During the procedure, the murderer is said to have not made eye contact with any of the victim's family members, which included Gaddis' mother, two brothers, and two other relatives.

"He's a coward just like when he shot my brother in the back of the head and he died a coward," the deceased officer's brother, Glen Gaddis, told reporters Wednesday night, according to the AP.

In addition to the family, several dozen police officers were reportedly also on hand to remember their fallen comrade.

On Tuesday, the Texas Board of Pardons and Paroles rejected Tamayo's request for clemency.

"It doesn't matter where you're from," Gov. Rick Perry spokeswoman Lucy Nashed said. "If you commit a despicable crime like this in Texas, you are subject to our state laws, including a fair trial by jury and the ultimate penalty."